1. Field of the Invention
The present invention relates to an actinic-ray- or radiation-sensitive resin composition employed in a semiconductor production process for an IC and the like, a circuit board production process for a liquid crystal, a thermal head and the like and other photofabrication processes, and also relates to a method of forming a pattern with the use of the composition. More particularly, the present invention relates to an actinic-ray- or radiation-sensitive resin composition that is suitable when, for example, far-ultraviolet rays of wavelength 250 nm or shorter, an electron beam or soft X-rays are used as an exposure radiation source, and also relates to a method of forming a pattern with the use of the composition.
2. Description of the Related Art
In recent years, the field of lithographic microfabrication of integrated circuits has seen increased demand for the achievement of ultrafine patterns of the order of tens of nanometers in order to realize high circuit density. This demand has led to a trend toward short-wavelength exposure—for example, from g-rays to i-rays and onward to KrF excimer laser light. At the same time, the development of lithography using an electron beam, X-rays or EUV light in addition to excimer laser light is also advancing.
In the case of microfabrication using a resist composition, not only is this being directly used in the manufacture of integrated circuits but, in recent years, has also been applied to the fabrication of so-called imprint mold structures, etc. (See, for example, patent references 1 and 2, and non-patent reference 1.)
Electron beam lithography in particular is now positioned as the next-generation or a future-generation pattern formation technology. Positive resists of high sensitivity and high resolution are needed for such lithography, increasing the sensitivity being an especially important matter with regard to reducing wafer processing time. However, increasing the sensitivity of positive resists to an electron beam is likely not only to reduce the resolving power but also to increase line edge roughness and degrade iso/dense bias. Thus, there is great demand for the development of resists in which none of these properties is compromised. Line edge roughness refers to the phenomenon wherein the edge at an interface of a resist pattern and substrate irregularly varies perpendicularly to the line because of the characteristics of the resist, so that viewed from above, the pattern edge appears uneven. This unevenness is transferred when etching using the resist as a mask, thereby causing poor electrical properties and hence poor yield. Especially in the ultrafine region of 0.25 μm or less, line edge roughness is now an extremely important area in which to achieve improvement. Iso/dense bias refers to the pattern dimension difference between an area of high resist pattern density and one of low resist pattern density. When this difference is great, the process margin is unfavorably narrow in the actual pattern formation. How to minimize this difference is an important aspect of resist technology development. Since there are trade-offs between high resolution, good pattern configuration, good line edge roughness and good iso/dense bias, how to achieve them all without compromise is a critical issue. This is also the case in lithography using X-rays or EUV light.
As a means for solving these problems, using a resin containing two types of repeating units that, when acted on by an acid, are decomposed to thereby generate an alkali-soluble group is now being studied (see, for example, patent reference 3). However, in the technology disclosed in patent reference 3, use was made of a composition comprising a photoacid generator and a resin containing two types of repeating units that when acted on by an acid, were decomposed to thereby generate an alkali-soluble group, so that it was difficult to simultaneously satisfy the requirements for sensitivity, resolution and line edge roughness in the ultrafine region.
Still further, using a resin containing a photoacid generator in its polymer side chain is being studied (see, for example, patent references 4 and 5). Patent reference 4 discloses a resin containing in its molecule both a photoacid generating group and a group whose solubility in an alkali developer is increased by acid decomposition. However, the sensitivity thereof in the exposure to EB or EUV could hardly be stated as being satisfactory. Patent reference 5 discloses a resin containing a photoacid generator with specified structure in its polymer side chain. However, the invention could not be stated as realizing good iso/dense bias.
As apparent from the above, the current situation is that the prior art technologies known to now cannot simultaneously fully satisfy the requirements for high sensitivity, high resolution, desirable pattern configuration, desirable line edge roughness, desirable iso/dense bias and the like in lithography using an electron beam, X-rays or EUV light.